The Speckled Rose of Oz by Donald Abbott
Another book set before the events of The Marvelous Land of Oz, Abbott gives the Scarecrow, Tin Woodman and Cowardly Lion another adventure as the wicked Poison Oak and Sir Wiley Gyle (brother of the Wicked Witches) try to turn Oz into a swamp by killing the Speckled Rose of Oz.
Abbott is imaginative here, even if the flow of his stories is still a bit too uneven. Not highly recommended, but not one to avoid either.
The Unwinged Monkey of Oz by Peter Schulenberg
Paramount the monkey has a problem: he was born without wings! Having had enough of feeling like he doesn't belong, he runs away from home and encounters some strange new friends, such as a man who inexplicably turns into a Gump but has no memory of either life, and a cavern full of people made of wet clay. Along the way, Paramount gets wind of a plot by a wicked witch and does what he can to stop her.
Schulenberg improves over past stories by including an antagonist. That said, the antagonist is defeated fairly easily. Still, Schulenberg definitely knows his Oz and clearly displays it here.
The Patchwork Bride of Oz by Gilbert M. Srague
A short story sees the Scarecrow and Scraps get married. There's a nice twist at the end.
Only complaint? It's far too short. It should have been a centerpiece in a book of short stories, not a book of its own. Still, if you can track it down, enjoy!